Starch-related Enzymes during Potato Tuber Dormancy and Sprouting
Sergeeva, L.I. ; Claassens, M.M.J. ; Jamar, D.C.L. ; Plas, L.H.W. van der; Vreugdenhil, D. - \ 2012
Russian Journal of Plant Physiology 59 (2012)4. - ISSN 1021-4437 - p. 556 - 564.
adp-glucose pyrophosphorylase - solanum-tuberosum - developmental-changes - hexose-phosphate - gene-expression - metabolism - sucrose - phosphorylase - biosynthesis - tuberization
Activities of enzymes presumably involved in starch biosynthesis (ADP-glucose pyrophosphorylase, AGPase) and/or breakdown (starch phosphorylase, STP; amylases) were determined during potato (Solanum tuberosum L.) tuber dormancy and sprouting. Overall activities of all these enzymes decreased during the first stage of tuber dormancy. No clear changes were detected at the time of dormancy breaking and sprouting. However, when AGPase activity was monitored by in situ staining during the entire dormancy period, a clear decrease during the dormant period and a large increase before visible sprouting could be observed. This increase was especially evident near the vascular tissue and at the apical bud, which showed a very intensive staining. In situ staining of STP activity in sprouting tubers showed that the tissue distribution of STP was the same as for AGPase. As a possible explanation, direct starch cycling is suggested: STP produces glucose-1-phosphate during starch breakdown, which can be directly used as a substrate by AGPase for starch synthesis. Gene expression studies with the AGPaseS promoter coupled to the firefly luciferase reporter gene also clearly showed a higher activity in sprouting tubers as compared to dormant tubers, with the highest expression levels observed around the apical buds. The presence of amylase activity at dormancy initiation and AGPase activity persistent at the sprouting stage suggest that starch was cycling throughout the entire dormancy period. According to the in situ studies, the AGPase activity increased well before visible sprout growth and could therefore be one of the first physiological determinants of dormancy breakage.
Differences in regulation of carbohydrate metabolism during early fruit development between domesticated tomato and two wild relatives
Kortstee, A.J. ; Appeldoorn, N.J.G. ; Oortwijn, M.E.P. ; Visser, R.G.F. - \ 2007
Planta 226 (2007)4. - ISSN 0032-0935 - p. 929 - 939.
accumulating lycopersicon-hirsutum - starch accumulation - sucrose synthase - quantitative trait - hexose-phosphate - sink metabolism - esculentum mill - invertase - expression - size
Early development and growth of fruit in the domesticated tomato Solanum lycopersicum cultivar Money Maker and two of its wild relatives, S. peruvianum LA0385 and S. habrochaites LA1777, were studied. Although small differences exist, the processes involved and the sequence of events in fruit development are similar in all three species. The growth of developing fruits is exponential and the relative growth rate accelerates from 5 days after pollination (DAP 5) to DAP 8, followed by a decline during further development. Growth is positively correlated to the standard ¿Brix plus starch¿¿ in the period DAP 8¿DAP 20. Carbohydrate composition and levels of sugars and organic acids differ in fruits of the wild accessions compared to domesticated tomato. The wild accessions accumulate sucrose instead of glucose and fructose, and ripe fruits contain higher levels of malate and citrate. The enzymes responsible for the accumulation of glucose and fructose in domesticated tomatoes are soluble invertase and sucrose synthase. The regulation of initial carbohydrate metabolism in the domesticated tomato differs from that in the wild species, as could be concluded from measuring activities of enzymes involved in primary carbohydrate metabolism. Furthermore, changes in the activity of several enzymes, e.g., cell wall invertase, soluble invertase, fructokinase and phosphoglucomutase, could be attributed to changes in gene expression level. For other enzymes, additional control mechanisms play a role in the developing tomato fruits. Localization by in-situ activity staining of enzymes showed comparable results for fruits of domesticated tomato and the wild accessions. However, in the pericarp of S. peruvianum, less activity staining of phosphogluco-isomerase, phosphoglucomutase and UDP-glucosepyrophosphorylase was observed.
Vacuolar invertase regulates elongation of Arabidopsis thaliana roots as revealed by QTL and mutant analysis.
Sergeeva, L.I. ; Keurentjes, J.J.B. ; Bentsink, L. ; Vonk, J. ; Plas, L.H.W. van der; Koornneef, M. ; Vreugdenhil, D. - \ 2006
Proceedings of the National Academy of Sciences of the United States of America 103 (2006)8. - ISSN 0027-8424 - p. 2994 - 2999.
quantitative trait loci - sucrose synthase - genetic-variation - developmental-changes - plant invertases - hexose-phosphate - enzymes - potato - expression - maize
The possible role of the sucrose-splitting enzymes sucrose synthase and invertase in elongating roots and hypocotyls of Arabidopsis was tested by using a combination of histochemical methods and quantitative trait locus (QTL) analysis. Lengths of roots and hypocotyls correlated better with invertase activities than with sucrose synthase activities. The highest correlations were observed with activities in the elongating zones of roots. The genetic basis of these correlations was studied by using QTL analysis. Several loci, affecting invertase activity, colocated with loci that had an effect on root or hypocotyl length. Further fine mapping of a major locus for root length, but not for hypocotyl length (top chromosome 1), consistently showed colocation with the locus for invertase activity containing a gene coding for a vacuolar invertase. The analysis of a functional knockout line confirmed the role of this invertase in root elongation, whereas other invertase genes might play a role in hypocotyl elongation. Thus, we show the power of QTL analysis, combined for morphological and biochemical traits, followed by fine-mapping and mutant analysis, in unraveling the function of genes and their role in growth and development
Comparing potato tuberization and sprouting: opposite phenomena
Vreugdenhil, D. - \ 2004
American Journal of Potato Research 81 (2004)4. - ISSN 1099-209X - p. 275 - 280.
solanum-tuberosum-l - gene-expression - developmental-changes - hexose-phosphate - abscisic-acid - dormancy - conversion - enzymes - sucrose - gibberellin
The regulation of tuber formation and tuber sprouting are compared. As a starting point it is hypothesized that these two phenomena are opposite to each other. This idea is tested from three points of view: hormonal regulation, gene expression, and carbohydrate metabolism. It is concluded that there is only limited evidence to support the hypothesis. On the contrary, several examples are given indicating that similar mechanisms might be operative during tuber formation and tuber sprouting.